An intelligent security assessment system includes a multiplicity of sens for detecting intrusion into an area. Each of the sensors operates on a different principle to detect intrusion. For example, sound, vibration, infrared, microwave and light level sensors are used. A computing system receives the outputs of each of the sensors and is programmed to provide an output based upon an algorithm that minimizes the likelihood of a false indication of intrusion by the intrusion sensors. Each sensor has an on and an off state and the computing system assigns a weighting factor for each sensor that is in the on state. The computing system sums the weighting factors and compares this sum to a reference and then provides a further output when the sum exceeds the reference. This computing system output is utilized to activate an additional intrusion detector such as an ultrasonic detection system and also to activate a video surveillance camera for observance of the area where the intrusion is indicated.